There is increasing evidence that the regulation of IL-1 and its natural receptor antagonist, namely the IL-1ra, represents a crucial step in the cascade of biochemical and cellular events contributing to the progression of persistence of inflammation. Administration of recombinant human IL-1ra reduces the severity of disease in animal models of lethal endotoxemia, sepsis, arthritis, colitis, graft-versus- host disease and insulin-dependent diabetes. In addition, preliminary studies have shown the efficacy of IL-1ra treatment in human septic shock and rheumatoid arthritis. This proposal will test the hypothesis that a dysregulation of intestinal IL-1 and IL-1ra may be a key mechanism of perpetuation of inflammation and tissue damage in inflammatory bowel disease (IBD). Recombinant human cytokines, specific non-cross-reacting radioimmunoassays (RIA), and DNA and RNA probes will be applied to tissue and cell preparations from patients with ulcerative colitis and Crohn's disease. Our extensive preliminary data suggest that the ratio of IL-1ra to IL-1 is significantly decreased in intestinal tissues and cells from IBD, that lamina propria mononuclear cells express both IL-1 and IL-1ra, and that intestinal epithelial cells produce large amounts of IL-1ra but not IL-1. The specific aims are to: 1) Determine the intestinal balance of IL-1 and IL-1ra in IBD. We will compare IL-1alpha, IL-1beta and IL-1ra levels in whole tissue, and lamina propria mononuclear cells and epithelial cells from control and IBD patients; 2) Determine the regulation of IL-1 and IL-1ra synthesis in intestinal mucosal cells. We will study which factors are involved in regulation of IL-1 and IL-ra synthesis; 3) Determine the cellular source of intestinal IL-1 and IL-1ra. Determination of the sites of IL- 1 and IL-1ra expression is an important issue. We will localize IL-1 and IL-1ra in intestinal tissue from control and IBD patients; 4) Assess the effects of exogenous IL-1ra on synthesis of other proinflammatory cytokines, including Il-6, IL-8 and TNF. We will test the hypothesis that IL-1 is a primary mediator of intestinal inflammation regulating the expression of other proinflammatory cytokines. Each study will involve extensive validation techniques, including comparison of RIA quantitation with ELISA, Northern blot analysis, immunohistochemistry and in situ hybridization techniques.